I guess this is where old DOS and the much hated "goto" offered
something beneficial. Adding a label to a line of code and then issuing
a goto to that label at the top of the script is better than the
alternatives. The label can be left in the code as it does no harm and
even acts as a bit of documentation. Removing or commenting the goto at
the top is obvious. Therefore only a one line change can undo this.

Your commenting suggestion can be dangerous as you'd have to remember
the range to undo it later. The if structure I've used is also inferior
as it requires you to comment or get rid of both the "if" and the "fi"
statements requiring 2 lines be changed.